1. Field
This patent specification relates to a charging method capable of charging a plurality of secondary battery-packs (herein after refereed to as a battery pack) such as lithium ion batteries. In particular, it relates to an optimal charging apparatus and method for charging spare (backup) battery packs used in an instrument body and mobile instrument, such as a mobile phone, a digital camera, etc.
2. Discussion of the Background
Due to smallness of a power supply capacity of a charging apparatus, a method of attaching and charging a plurality of battery packs one after another in the charging apparatus has been practiced, and many patent applications thereabout has been filed. Even though the term xe2x80x9ca batteryxe2x80x9d is utilized in the below described literature, plural batteries serially arranged are generally used as a battery pack, because the voltage per cell of this type of secondary battery is small.
For example, Japanese Patent Application Laid Open No. 56-110446 discloses a technology for efficiently charging normal batteries by skipping a battery that expresses abnormally lower voltage during charging. Japanese Patent Application Laid Open No. 56-166731 discloses a technology for charging an inert battery in a similar manner to a normal battery by separately and sequentially charging a plurality of batteries one after another, using a charging control mechanism when controlling charging of each battery. Japanese Utility Model Application Publication No. 4-24759 discloses a charging apparatus that charges a plurality of batteries one after another while detecting completion of charging of each battery. Such an apparatus detects attachment, and initializes and proceeds to charge the uncharged batteries when the uncharged battery is attached. Japanese Patent Application Laid Open No. 7-130399 refers to a technology capable of shortening a charging time period by stopping charging when temperature of a battery in the course of being charged exceeds a prescribed level, then charging the next one, and re-starting charging of the former battery when temperature of the next battery exceeds a prescribed level.
According to these former two applications, charging of an additional uncharged battery must be initiated by freshly attaching the uncharged battery after the entire batteries has been charged, because detection of the uncharged battery is impossible if the uncharged battery is newly attached during charging. The charging apparatus of Japanese Utility Model Application Publication No. 4-24759 inconveniently recharges a charged battery which does not require additional charging, because the charging apparatus returns to an initial condition and starts charging again restarting from the first battery when an uncharged battery is attached, even though the uncharged battery is charged. Although a time period for charging the entire batteries is advantageously shortened, the technology of Japanese Patent Application Laid Open No. 7-130399 takes a long time period in completing charging of the first battery in comparison with a case when charging one by one. Further, since an uncharged battery is not detected, charging can be started only by freshly attaching the uncharged battery after charging of the entire batteries has been completed, similar to the technology of Japanese Patent Application Laid Open No. 56-166731 or the like. Further, a conventional charging apparatus itself typically is bulky and costly, because a control circuit for charge control use in the conventional apparatus is entirely built therein.
Accordingly, an object of the present specification is to address and resolve the above-noted and other problems and provide a new battery pack charging apparatus. The above and other objects are achieved according to the present specification by providing a novel battery pack charging apparatus that charges in turn a plurality of battery packs which are attached to the apparatus. The novel battery pack charging apparatus, according to one embodiment, includes a switching device operative to switch the plurality of battery packs and select a battery pack to be charged, a charging circuit configured to charge the selected battery pack, a charging manner setting circuit operative to set any one of constant current charging and constant voltage charging to be executed by the charging circuit during charging, a battery pack voltage detecting circuit configured to detect a voltage of the selected battery pack, a charge current detecting circuit configured to detect a current during charging, a battery pack attachment detecting circuit configured to detect an attachment condition of a battery pack, and a memory configured to store detachment and attachment history data of a battery pack based on an attachment condition detected by the battery pack attachment detecting circuit. A battery pack to be charged next and charging manner therefor may be determined in accordance with the detachment and attachment history data in the memory and the voltage detected by the battery pack voltage detecting circuit, after current charging to a battery pack is completed.
In another embodiment, a preparatory charging process is continued for the battery pack until the detected voltage of the battery pack increases to a first voltage level after the detected voltage is lower than the first voltage level. A constant current charging process is performed until the detected voltage of the battery pack grows up to a second voltage level when the detected voltage is higher than the first voltage level, and a constant voltage charging process is performed until charge current flowing through a battery pack becomes less than a prescribed current after the voltage of the battery. pack has reached the second voltage level.
In yet another embodiment, when another battery pack has been attached to the charging apparatus before current charging to the battery pack is completed, the other battery pack is selected by the switching device, and detachment and attachment history data related to the other battery pack is read from the memory. When the other battery pack is additionally attached, charging thereto is performed by starting from a determination process for determining whether the detected voltage of the other battery pack is higher or lower than the first voltage level.
In yet another embodiment, when the other battery pack has been already attached before current charging to the battery pack has been completed and the detected voltage is lower than a third voltage level, constant current charging is performed thereto.
In yet another embodiment when the other battery pack has already been attached and the voltage is higher than the third voltage level, charging is omitted and it is detected if still another battery pack has been attached.
In yet another embodiment, an attachment condition is always monitored by the battery pack attachment detecting circuit after current charging to the battery pack has been completed, and when another battery pack has not been attached, the voltage of the battery pack to which charging is completed is detected, and when the detected voltage is lower than the third voltage level, charging to the battery pack is started from the constant current charging process.
In yet another embodiment, at least one battery pack among the plural battery packs is built in a prescribed instrument body, and other battery packs are for backup use.
In yet another embodiment, the battery pack built in the prescribed instrument body is charged in preference to the other battery packs.
In yet another embodiment, the charging manner setting circuit is included in the prescribed instrument body.